Does a hen go broody while she is laying a clutch or after she has layed a clutch?

Does a hen go broody while she is laying a clutch or after she has layed a clutch? I have a chicken that has been sitting in a box for a few hours. She didn't come to get her food like the other chickens.

They usually lay a clutch first. She won't lay ANY eggs once she goes broody. She'll go broody when the hormones kick in whether there are eggs or not.
Hope this answers your questions. She may just have been taking longer to lay.
A broody is unmistakable. She will stay on the nest day and night (except for a 1/2 hour daily foray) and growl if disturbed.